Supports, including scaffolding and planks, are used commonly to support maintenance personnel above a surface. For example, supports supported by step or trestle ladders are used on extension ladders while the sides are supported by ladder jacks are commonly used by siding and painting contractors.
The size of the support surface required, that is, the surface on which maintenance personnel can stand to perform maintenance, varies with circumstances. Accordingly, a support has been provided that can be adjusted to vary the size of its support surface. Specifically, the support is formed from two sections that are slidably engaged with each other. The sections can be slid together or apart to adjust the size of the support surface. However, the relative position of the support sections cannot be fixed, and the sections can slide with respect to each other during use.
Accordingly, there exists a need for an extendable support or plank the size of whose support surface can be fixed during use and positively locked in place. A friction locking extension plank by Ransara of Japan relies on friction to maintain the desired size of the extension plank.